1. Field of the Invention
The present invention relates to an electric connector for use in making a required electric connection between printed circuit boards, between a printed circuit board and a selected device in a computer, or between a printed circuit board and a server or backboard package, and more particularly to an electric connector for use in transmitting high-frequency signals.
2. Related Art
Referring to FIG. 10, a conventional electric connector 11 has a plurality of pair sets of 12 signal terminals 12a and 12b for transmitting high-speed signals in differential transmission ways, thereby significantly reducing noise signals. More specifically, if cross talk appears between the pair of signal terminals 12a and 12b, unwanted signals of the same phase can be cancelled. Also, a ground terminal 13 is arranged between adjacent pair sets 12 of the signal terminals, thereby preventing cross talk from appearing in adjacent pair sets of signal terminals.
Such a conventional electric connector uses extra ground terminals, and accordingly the number of parts to be assembled, and hence, the manufacturing cost will increase. The more the terminal-loading density increases, the narrower the distance between the ground terminal 13 and the signal terminal 12a or 12b of either adjacent pair set decreases, and the larger the signal energy will be lost by the nearby ground terminal 13. Thus, the insertion loss which is caused by inserting the electric connector in the signal-transmitting circuit increases.
The inter-distance “b” between adjacent signal terminals in each pair set decreases, and accordingly the thickness of the signal terminal is reduced. Disadvantageously such thin signal terminals are apt to be deformed or bent in press fitting in selected terminal slots in the connector body.
The signal terminals 12a and 12b of each set are arranged vertically at different levels. Therefore, the upper conductor 12a extending from the upper level to an associated printed circuit board at the lowest level is longer than the lower conductor 12b extending from the lower level to the printed circuit board. As a result the electric signals traveling such different lengths of conductors 12a and 12b reach the printed circuit board at different times, thus causing noises from the electric signals which appear in the pair set of signal terminals 12a and 12b. 
One object of the present invention is to provide a high-frequency electric connector which is free of such defects as described above.